An organic light emitting element (organic electroluminescence element or organic EL element) is an electronic element including a pair of electrodes and an organic compound layer placed between the pair of electrodes. An electron and a hole are injected from the pair of electrodes, and then the electron and the hole recombine in the organic compound layer to produce an exciton of a luminous organic compound. The organic light emitting element emits light upon return of the exciton to its ground state.
A method of improving the light emitting efficiency of the organic EL element is, for example, a method involving utilizing a triplet excited state. Several specific methods each involving utilizing the triplet excited state have been currently proposed. At present, however, it is difficult to keep an exciton produced in the organic EL element trapped in a layer responsible for light emission. Accordingly, various kinds of research and development have been performed to overcome the difficulty.
PTL 1 proposes, as a compound for trapping an exciton in a specific layer (such as an emission layer), a compound having a silsesquioxane structure, specifically, Compounds a-1 and b-1 shown below.

Here, the silsesquioxane compounds (Compound a-1 and Compound b-1) proposed in PTL 1 are each a compound that has a high ratio of an aryl group to a silsesquioxane unit, has a high absorbance, and can easily stack between its molecules.